.\" Copyright, Bruno Haible <haible@clisp.cons.org>
.\" Copyright 2024, Alejandro Colomar <alx@kernel.org>
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" References consulted:
.\"   GNU glibc-2 source code and manual
.\"   Dinkumware C library reference http://www.dinkumware.com/
.\"   OpenGroup's Single UNIX specification http://www.UNIX-systems.org/online.html
.\"   ISO/IEC 9899:1999
.\"
.TH mbstate_t 3type 2024-05-03 "Linux man-pages 6.9.1"
.SH NAME
mbstate_t
\-
multi-byte-character conversion state
.SH LIBRARY
Standard C library
.RI ( libc )
.SH SYNOPSIS
.nf
.B #include <wchar.h>
.P
.BR typedef " /* ... */  " mbstate_t;
.fi
.SH DESCRIPTION
Character conversion between the multibyte representation and the wide
character representation uses conversion state, of type
.IR mbstate_t .
Conversion of a string uses a finite-state machine; when it is interrupted
after the complete conversion of a number of characters, it may need to
save a state for processing the remaining characters.
Such a conversion
state is needed for the sake of encodings such as ISO/IEC\~2022 and UTF-7.
.P
The initial state is the state at the beginning of conversion of a string.
There are two kinds of state: the one used by multibyte to wide character
conversion functions, such as
.BR mbsrtowcs (3),
and the one used by wide
character to multibyte conversion functions, such as
.BR wcsrtombs (3),
but they both fit in a
.IR mbstate_t ,
and they both have the same
representation for an initial state.
.P
For 8-bit encodings, all states are equivalent to the initial state.
For multibyte encodings like UTF-8, EUC-*, BIG5, or SJIS, the wide character
to multibyte conversion functions never produce non-initial states, but the
multibyte to wide-character conversion functions like
.BR mbrtowc (3)
do
produce non-initial states when interrupted in the middle of a character.
.P
One possible way to create an
.I mbstate_t
in initial state is to set it to zero:
.P
.in +4n
.EX
mbstate_t state;
memset(&state, 0, sizeof(state));
.EE
.in
.P
On Linux, the following works as well, but might generate compiler warnings:
.P
.in +4n
.EX
mbstate_t state = { 0 };
.EE
.in
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
C99, POSIX.1-2001.
.SH SEE ALSO
.BR mbrlen (3),
.BR mbrtowc (3),
.BR mbsinit (3),
.BR mbsrtowcs (3),
.BR wcrtomb (3),
.BR wcsrtombs (3)
